Allow hugs and kisses to give effects

[GeorgH93]

Description:

It should be possible to apply custom effects when a player hugs or kisses his/her partner. Effect suggestions:

• Sharing the health between the partners (new hp = (sum of hp of both players) / 2)
• Healing the kissed player by a configurable amount

Implementation:

• [ ] Add events to the API
  • [ ] Kissed event
  • [ ] Hugged event
• [ ] Move particle effect into the newly created event
• [ ] Add new effects
  • [ ] Health share
    • [ ] Add config option
    • [ ] Apply effect
  • [ ] Heal
    • [ ] Add config option
    • [ ] Apply effect